1. Field of the Invention
This invention relates to an air dryer device for drying compressed air of a compressed air system, such as an air brake, for a vehicle.
2. Prior Art
A conventional air dryer device under consideration comprises a drain valve mounted on a lower portion of a dryer housing for discharging water condensed from water vapor of compressed air supplied from a compressor to the air dryer device. Generally, the drain valve is automatically opened to discharge the water upon application of a pneumatic signal from an air governor to the drain valve.
In winter or in cold climates, the water remaining on the drain valve near its valve element is susceptible to freezing so that the drain valve can not be operated properly. In order to overcome this freezing, an electric heater has heretofore been mounted near the drain valve, the electric heater being powered by a battery of the vehicle. The heater in the form of a rod is received in a hole formed in the body of the drain valve. Therefore, the heat generated by the heater is transmitted to the valve body and is radiated to the ambient atmosphere since the drain valve body is made of metal of a high heat conductivity such as aluminum. Thus, the heat generated by the heater is subjected to a substantial loss. To compensate for such a heat loss, the capacity of the heater as well as the capacity of the battery must be increased.